Patent CZ-296088-B6 (CZ)
Title: Method of and system for measuring shape of joint track, particularly of mandible
IPC: A61C19/045
Filed: 2003-01-31
Abstract: The present invention relates to a method of measuring shape of joint track, particularly of mandible, the method comprising making a solid spatial target (1) for the mandible, a target (2) for the maxilla and a target (3) of an occlusion plane formed by a plate attached thereto. On the surface of said plate a plurality of RF (100, 200, 300) reference points are marked. A coordinate system SS (10, 20, and 30) is then assigned to each target (1, 2, and 3). Subsequently a spatial position of all the reference points RF (100, 200, and 300) is measured close to each target (1, 2, and 3). The measured coordinates are then stored in a memory. When measuring position of the RF (300) of the occlusion plane target (3), there are also measured coordinates of the occlusion plane within the space of the same SS (30) and are stored in the memory, too. Further, there is measured a distance (L) of both the left-hand and right-hand jaw joint heads (6, 7), the target (2) is attached to the maxilla (9), and the occlusion plane plate (11), having the target (3) attached thereto, is inserted between the maxilla (9) and the mandible (8). At occlusion, there is taken a picture of the target (2) and the target (3), in which picture, there are localized and identified pictures RF (200, 300) on the target (2) and the target (3). Using those RF (200, 300) pictures and independently measured spatial coordinates thereof, a pick-up camera (5) is calibrated. Subsequently mutual position of the camera (5) SS (50) and upper target (2) SS (20) and at the same time a mutual position of the camera (5) SS (50) and the target (3) SS (30). Using this data and knowing position of the occlusion plane in the target (3) SS (30), there is determined the position of the occlusion plane in the target (1) SS (10). The target (3) and the plate (11) are removed, the target (1) is attached to the mandible (8) (1) and when opening and closing the jaws (8, 9) a sequence of pictures of both the targets (3, 1) is scanned. For each scanned picture, there are localized and identified pictures RF (300, 100) and based on the RF (200) or RF (100 points on the target (2) or target (1) and independently measured coordinates thereof, there is carried out a separate calibration of the camera (5) for each target. Subsequently the mutual position SS of targets (1, 2) of the mandible and maxilla is determined for each picture. From mutual positions of mandible and maxilla (8, 9) when opening mouth, there is determined axis (12) of rotation about the left-hand and right-hand joints in the target (1) SS (10), wherein said axis (12) represents an axis connecting centers of the left-hand and right-hand joint heads (6, 7) and this axis (12) of rotation and the occlusion plane along with a selected start on the axis (12) of rotation define SS of a head, after definition of which selected movements of the mandible (8) are carried out. For each movement several pictures of the targets (1, 2) are taken, in each picture a mutual position of mandible and maxilla (8, 9) is evaluated and is transferred to the head SS. Positions of the joint heads (6, 7) during motion are determined and a shape of a joint track of mandible (8) is then determined therefrom.